Laboratory of NMR Spectroscopy, Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland.
J Phys Chem A. 2010 Feb 25;114(7):2471-5. doi: 10.1021/jp9096056.
Exploring the relation between shielding constants, resonance frequencies and magnetic moments of the nuclei we demonstrate that nuclear magnetic shielding can be directly observed from NMR spectra. In this approach, the absolute shielding constants of all the nuclei can be related to a single reference scale, with atomic (3)He as the primary standard. The accuracy of the data obtained using our method is confirmed comparing the (1)H and (13)C shielding constants for a series of deuterated compounds with those determined analyzing the traditional chemical shifts. Since the use of helium-3 is not in general a practical alternative, we next transfer the reference standard to the (2)H signals of external lock solvents, in this way making the method easy and ready for application with most NMR spectrometers. Finally, we illustrate our new method with the measurements of the (2/1)H primary isotope effects in several liquid deuterated solvents.
探索屏蔽常数、核的共振频率和磁矩之间的关系，我们证明了核磁共振谱可以直接观察到核磁共振屏蔽。在这种方法中，所有核的绝对屏蔽常数都可以与一个单一的参考尺度相关联，以原子（3）He 作为主要标准。通过比较一系列氘代化合物的氢和碳的屏蔽常数与通过分析传统化学位移确定的值，证实了我们方法所获得的数据的准确性。由于氦-3的使用通常不是一种实际的选择，我们接下来将参考标准转移到外部锁定溶剂的（2）H 信号，这样使方法变得简单易用，并且可以与大多数 NMR 光谱仪一起使用。最后，我们用几种液体氘代溶剂中的（2/1）H 主要同位素效应的测量来举例说明我们的新方法。
